# US 12,113,125 B2 · Bipolar transistor having collector with doping concentration discontinuity > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,113,125 B2 - Document ID: US12113125B2 - Status: Granted - Kind: B2 - Application number: 17/809,855 - Filed: 2022-06-29 - Published: 2023-01-05 - Granted: 2024-10-08 - Earliest claimed: 2021-06-30 - Assignees: Skyworks Solutions, Inc. - Applicants: Skyworks Solutions, Inc. - Inventors: Kai Hay Kwok; Cristian Cismaru; Andre G. Metzger; Guoliang Zhou - Web page: https://patentgrep.com/patent/US12113125B2 ## CPC - H10D 10/821: {Vertical heterojunction BJTs} - H10D 62/137: {Collector regions of BJTs} - H10D 62/60: Impurity distributions or concentrations - H10D 62/824: comprising only Group III-V materials heterojunctions, e.g. GaN/AlGaN heterojunctions - H10D 62/85: being Group III-V materials, e.g. GaAs - H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES ## Abstract This disclosure relates to bipolar transistors, such as heterojunction bipolar transistors, having increased collector thickness for improved ruggedness. In some embodiments, the collector thickness can be above 1.1 microns. The collector can have at least one doping concentration grading. The collector can have a high doping concentration at a junction between the collector and the sub-collector, such as at the high end of the grading. In some embodiments, the high doping concentration can be above about 9×1016 cm−3. The collector can include a region with high doping concentration adjacent the base. The collector can include a discontinuity in the doping concentration, such as at the low end of the grading. Such bipolar transistors can be implemented, for example, in power amplifiers. ## Claims ### Claim 1 A bipolar transistor comprising: an emitter; a base; and a collector having a first collector region and a second collector region, the first collector region between the base and the second collector region, the first collector region having a flat doping concentration, the second collector region having a graded doping concentration that increases along a direction away from the base, a transition from the flat doping concentration of the first collector region to the graded doping concentration of the second collector region having a step increase in the doping concentration, the collector having an additional collector region between the base and the first collector region, and the additional collector region having a doping concentration that is higher than the doping concentrations of the first collector region and the second collector region. ### Claim 2 (depends on 1) The bipolar transistor of claim 1, wherein the step has a doping concentration increase of at least about 2×1016 cm−3. ### Claim 3 (depends on 1) The bipolar transistor of claim 1, wherein the step has a doping concentration increase in a range of about 2.5×1016 cm−3 to about 8.25×1016 cm−3. ### Claim 4 (depends on 1) The bipolar transistor of claim 1, wherein there is a step decrease in the doping concentration across the transition from the additional collector region and the first collector region. ### Claim 5 (depends on 1) The bipolar transistor of claim 1, wherein the collector has a thickness of more than 1.1 microns. ### Claim 6 (depends on 1) The bipolar transistor of claim 1, wherein the collector has a thickness in a range from about 1.2 microns to about 1.5 microns. ### Claim 7 (depends on 1) The bipolar transistor of claim 1, wherein the second collector region has maximum doping concentration that is larger than 9×1016 cm−3. ### Claim 8 (depends on 1) The bipolar transistor of claim 1, wherein the second collector region has a maximum doping concentration that is in a range of about 1×1017 cm−3 to about 5×1017 cm−3. ### Claim 9 (depends on 1) The bipolar transistor of claim 1, wherein a maximum doping concentration of the second collector region is at least 13 times greater than a doping concentration of the first collector region. ### Claim 10 (depends on 1) The bipolar transistor of claim 1, wherein the second collector region has a thickness of at least about 0.7 microns. ### Claim 11 (depends on 1) The bipolar transistor of claim 1, wherein the first collector region and the second collector region have a combined thickness in a range from about 1.2 microns to about 1.5 microns. ### Claim 12 (depends on 1) The bipolar transistor of claim 1, wherein the second collector region has a maximum doping concentration that is in a range of about 1.5×1017 cm−3 to about 5×1017 cm−3. ### Claim 13 A bipolar transistor comprising: an emitter; a base; and a collector, the base between the collector and the emitter, the collector having a gradient doping concentration and a discontinuity between the gradient doping concentration and a lower doping concentration, the collector having a doping spike having a doping concentration that is higher than the gradient doping concentration, the lower doping concentration between the doping spike and the gradient doping concentration. ### Claim 14 (depends on 13) The bipolar transistor of claim 13, wherein the discontinuity includes a step in the doping concentration of at least about 2×1016 cm−3. ### Claim 15 (depends on 13) The bipolar transistor of claim 13, wherein the discontinuity includes a step in the doping concentration in a range of about 2.5×1016 cm−3 to about 8.25×1016 cm−3. ### Claim 16 (depends on 13) The bipolar transistor of claim 13, wherein the collector has a discontinuity between the doping spike and the lower doping concentration. ### Claim 17 (depends on 13) The bipolar transistor of claim 13, wherein the collector has a thickness of more than 1.1 microns. ### Claim 18 (depends on 13) The bipolar transistor of claim 13, wherein the collector has a thickness in a range from about 1.2 microns to about 1.5 microns. ### Claim 19 (depends on 13) The bipolar transistor of claim 13, wherein the gradient doping concentration has a maximum doping concentration that is larger than 9×1016 cm−3. ### Claim 20 (depends on 13) The bipolar transistor of claim 13, wherein the gradient doping concentration has a maximum doping concentration that is in a range of about 1×1017 cm−3 to about 5×1017 cm−3. ### Claim 21 (depends on 13) The bipolar transistor of claim 13, wherein the gradient doping concentration has a maximum doping concentration that is at least 13 times greater than the lower doping concentration. ### Claim 22 (depends on 13) The bipolar transistor of claim 13, further comprising a sub-collector, the collector between the base and the sub-collector. ### Claim 23 (depends on 13) The bipolar transistor of claim 13, wherein the bipolar transistor is a heterojunction bipolar transistor (HBT). ### Claim 24 (depends on 13) The bipolar transistor of claim 13, wherein the bipolar transistor is a GaAs-based transistor. ### Claim 25 (depends on 13) A power amplifier comprising a bipolar transistor of claim 13. ### Claim 26 (depends on 24) A mobile or fixed wireless device comprising an antenna, a battery, and the power amplifier of claim 24. ### Claim 27 (depends on 13) The bipolar transistor of claim 13, wherein a region of the collector that has the gradient doping concentration has a thickness of at least about 0.7 microns. ### Claim 28 (depends on 13) The bipolar transistor of claim 13, wherein the gradient doping concentration has a maximum doping concentration that is in a range of about 1.5×1017 cm−3 to about 5×1017 cm−3.